Java，从文件中获取特定的字符串[重复]

Question

这个问题在这里已有答案：

• How to read a single line from file in java 3回答
• Java: Getting a substring from a string starting after a particular character 9个答案
• How to extract a substring using regex 10个答案

我想从Text文件中获取特定的String。

例如，我只希望将指定的部分（第3行）保存在新文件中

19:22:08.999 T:5804  NOTICE: Aero is enabled
19:22:08.999 T:5804  NOTICE: special://xbmc/ is mapped to: C:\Program Files (x86)\Kodi
19:22:08.999 T:5804  NOTICE: key://xbmcbin/ is mapped to: C:\Program Files (x86)\Kodi
     I want this part -----> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
19:22:08.999 T:5804  NOTICE: special://xbmcbinaddons/ is mapped to: C:\Program Files (x86)\Kodi/addons

我的代码：

public static void main(String[] args) throws IOException {
    ArrayList<String> result = new ArrayList<>();
    Scanner s = null; 
    try { 

        s = new Scanner(new BufferedReader(new FileReader("C:/test.txt"))); 

        while (s.hasNextLine()) {
            result.add(s.nextLine());
        }
    } finally {
        if (s != null){
            s.close();
        }
    } System.out.println(result);
} 

我把所有东西保存在一个ArrayList中，但我现在怎么样

1. 仅保存此ArrayList的一个元素
2. 仅保存变量或新文件中的部分行（粗体）。

编辑我解决了一切非常感谢你的帮助，特别是@dustytrash

Answer 1

您检查每一行以查看它是否包含您需要的值。当您找到该值时，您可以停止扫描（假设您只需要查找1行）。然后，您可以根据需要解析该行。

根据您的示例，以下生成的'key：// xbmcbin /映射到：C：\ Program Files（x86）\ Kodi'：

public static void main(String[] args) throws IOException 
{
    String result = "";
    Scanner s = null; 
    try 
    {
        final String searchKey = "key:";
        final String trimFromLine = "Kodi";
        s = new Scanner(new BufferedReader(new FileReader("test.txt"))); 

        while (s.hasNextLine() && result.isEmpty()) 
        {
            String nextLine = s.nextLine();
            if (nextLine.contains(searchKey))
            {
                // Trim everything from the end, to the beginning character of our searchKey (in this case 'key:')
                result = nextLine.substring(nextLine.indexOf(searchKey));

                // Take everything from the beginning to the end of the beginning character in our trimFromLine (in the case start index of 'Kodi')
                result = result.substring(0, result.indexOf(trimFromLine));
            }
        }
    } 
    finally 
    {
        if (s != null)
        {
            s.close();
        }
    } System.out.println(result);
}